The human anatomy includes many types of tissues that can either voluntarily or involuntarily, perform certain functions. After disease, injury, or natural defects, certain tissues may no longer operate within general anatomical norms. For example, after disease, injury, time, or combinations thereof, the heart muscle may begin to experience certain failures or deficiencies. Certain failures or deficiencies can be corrected or treated with implantable medical devices (IMDs), such as implantable pacemakers, implantable cardioverter defibrillator (ICD) devices, cardiac resynchronization therapy defibrillator devices, or combinations thereof.
IMDs detect and deliver therapy for a variety of medical conditions in patients. IMDs include implantable pulse generators (IPGs) or implantable cardioverter-defibrillators (ICDs) that deliver electrical stimuli to tissue of a patient. ICDs typically comprise, inter alia, a control module, a capacitor, and a battery that are housed in a hermetically sealed container with a lead extending therefrom. It is generally known that the hermetically sealed container can be implanted in a selected portion of the anatomical structure, such as in a chest or abdominal wall, and the lead tip portion can be positioned at the selected position near or in the muscle group. When therapy is required by a patient, the control module signals the battery to charge the capacitor, which in turn discharges electrical stimuli to tissue of a patient via electrodes disposed on the lead, e.g., typically near the distal end of the lead. Typically, a medical electrical lead includes a flexible elongated body with one or more insulated elongated conductors. Each conductor electrically couples a sensing and/or a stimulation electrode of the lead to the control module through a connector module.
In order to deliver stimulation or to perform sensing functions, it is desirable for the distal end of a medical electrical lead to substantially remain in its position, as originally implanted by a physician. Leads are typically implanted endocardially such that the lead is transvenously introduced with the distal end of the lead positioned in one of the chambers. In contrast to endocardial leads, epicardial leads are introduced outside of the cardiovascular system to bring the distal end in contact with the epicardial or myocardial tissue. Numerous scenarios exist in which epicardial leads are preferred over endocardial leads such as when patients possess inadequate vascular access. Children, for example, may require an epicaridal lead instead of an endocardial lead. Additionally, some congenital heart disease patients require the use of an epicardial lead. Moreover, patients in which placement of a lead through the coronary sinus for delivery of cardiac resynchronization therapy that has failed may benefit by placement of an epicardial lead in a more optimal pacing site location such as the outer surface of the heart.
Epicardial lead implantation requires surgical access to allow sufficient room to position and fixate the pacing lead by either sutures or a right angle helical screw component. Surgical access is more traumatic and requires longer recovery time as compared to percutaneous implant methods. One such percutaneous implant method has been described in Subxiphoid Approach to Epicardial Implantation of Implantable Cardioverter Defibrillators in Children, Sertac Haydin, M. D. et al. PACE, Vol. 00 (2013). In the Haydin article, a transvenous ICD lead was introduced through a subxiphoid percutaneous approach such that the extendable-retractable helix was screwed into non-cardiac tissue for fixation without pacing or sensing capability through the ICD lead.
Another epicardial implantation method is described in U.S. Pat. No. 5,443,492 to Stokes et al. which involves an epicardial lead in which an active fixation mechanism secures the lead in place while allowing a distal electrode on the lead to mechanically “float” with respect to the body tissue. The active fixation mechanism comprises a curved hook disposed at the distal end of the lead. The curved hook defines a helix around at least a portion of the lead's circumference. A hollow introducer needle is slidably disposed on the lead. The hollow needle provided with a longitudinal slit in a distal section of is length, such that the distal section of the needle can be advanced over the distal end of the lead, past the fixation hook, which is received in the longitudinal slit.
The Stokes et al. lead is unable to be fixated solely in the epicardial tissue since the lead penetrates beyond the epicardium, and resides mid-myocardial for stimulation. This is due to the hollow needle that interlocks with the side hook. The needle is jabbed into the surface driving the tip (i.e. electrode) of the lead deeply into the heart myocardium. The needle is then twisted or torqued (i.e. bayonet style) into the tissue. Thereafter, the needle is withdrawn leaving the lead tip disposed intramyocardial.
Numerous other lead configurations have employed side helical fixation members such as U.S. Pat. No. 8,755,909 B2 to Sommer et al. incorporated by reference in its entirety. One type of left lead adapted for placement in the coronary vasculature is that disclosed in U.S. Pat. No. 7,860,580, issued to Sommer, et al. and incorporated herein by reference in its entirety. Another type of left lead adapted for placement in the coronary vasculature is that disclosed in U.S. Pat. No. 7,532,939, issued to Sommer, et al. and also incorporated herein by reference in its entirety. The side helixes from Sommer cannot be used to solely attach to epicardial tissue since the free end of the Sommer side helix is configured to engage thinner tissue for coronary vein fixation.
Additional designs for a side-helix leads are disclosed in U.S. Pat. No. 5,443,492, issued to Stokes, et al. U.S. Pat. No. 7,529,584, issued to Laske, et al, U.S. Pat. No. 7,313,445, issued to McVenes, et al., U.S. Pat. No. 6,493,591, issued to Stokes, U.S. Pat. No. 6,556,874, issued to Audoglio, all of which are incorporated herein in their entireties.
It is desirable to develop a medical electrical lead that minimizes trauma to the tissue and solely attaches to the epicardial tissue.